Santa Fe Dehumidifier 8" Flex Insulated Duct 25' (4020177) is an optional add-on to these dehumidifiers: Compact 2 and Classic. Duct work is useful if you need to hide the dehumidifier, need to dehumidify an otherwise inaccessible area or pump air from one room to another. It is 25 foot long with a diameter of 8 inches, that is durable and long lasting that will accommodate most situations because the duct is flexible. This flex duct is only one out of the other parts needed to duct the dehumidifiers. Some parts that you may need - ducting collars, register grill and register head are sold separately. The insulation of the duct keeps the dehumidifier more energy efficient.